Field of Invention
The present invention relates to scintillator screens for use in digital radiography.
Background
Systems for acquiring radiographic images are widely used in medical and dental care. Due to recent advances in component miniaturization, data transmission and processing speed with improved image processing and display capabilities, apparatus and methods for obtaining radiographic images directly in digital format are increasingly being used. With digital radiography, the radiation image exposures captured on radiation-sensitive phosphor layers are converted, pixel by pixel, to electronic image data, which is then stored in memory circuitry for subsequent read-out and display on suitable electronic image display devices.
In typical digital radiography of the indirect type, a radiation sensing material, more generally termed a phosphor layer or scintillator, converts incident x-rays to visible light, which is then detected by a photosensor array that converts light intensity information to a corresponding electronic image signal.
Columnar, thallium doped cesium iodide (CsI) phosphors are widely used in scintillator screens in digital radiography. Thallium doped CsI provides an excellent combination of high x-ray absorptivity over a wide energy range, and high scintillation efficiency, while the columnar structure allows for a maintaining high spatial resolution at high x-ray stopping power. As a result, from an image quality perspective, these columnar, thallium doped CsI screens are used in many radiographic applications.
It is generally accepted that these CsI based columnar scintillator screens have the potential to provide the highest spatial resolution needed for any radiographic application. However, it is difficult to fully realize this potential in practical applications due the mechanical and environmental fragility of CsI. CsI crystals are highly water-soluble and hence these scintillators must to be maintained in sealed environments. Further, CsI crystals are columnar structures and are mechanically fragile requiring shock resistant containers. As a result the cost structure is quite high for applications using columnar CsI scintillator screens.
As a result scintillator screens having an image quality approaching that of columnar, thallium doped CsI scintillator screens, and are significantly less costly or less sensitive to mechanical shock and environmental conditions are desired.